Recently, distance measuring apparatuses such as laser radars have been used not only for measuring a distance to an object but also in various scenes such as for the purposes of monitoring surroundings, for example, detecting obstacles for an automobile or detecting a person between doors for automatic platform gates and cars of a train at a railroad platform.
For such distance measuring apparatuses, a desire for increasing a measurement range for measuring the object is expected to grow. To address this, it is conceivable that a distance measuring apparatus is equipped with a projection system using an optical system that increases a light projection range, and with a wide-angle lens used as a condenser lens. In this case, however, noise light incident on the condenser lens also increases, and accordingly a signal-to-noise (S/N) ratio decreases. Thus, it is conceivable to use a photodetector array to selectively use outputs of photodetectors in an area irradiated with optical feedback from the measurement object (see Japanese Laid-open Patent Publication No. 2004-157044).